Monthly Archives: April 2016

Contributing a Golay encoder/decoder to codec2

I’ve been following the development of FreeDV, a libre very-low bitrate digital voice system for amateur radio. Central to this is codec2, the codec used in the system. A few days ago a thread popped on the [codec2-dev] mailing list that the existing implementation of binary Golay codes was not (L)GPL compatible and that a replacement was needed. Since I’ve held a bit of an interest in forward error correction (FEC) lately I decided to take a stab at reimplementation.

The implementation ended up not taking terribly long. The main issue was that the old decoder would shift the return value of golay23_decode() left 11 bits compared to golay23_encode() whereas my initial attempt would do the most obvious thing, having golay23_decode(golay23_encode(x)) == x. But once I figured this out the rest was trivial.

The result of my efforts can now be seen in golay32.c on the codec2-dev SVN. This whole thing is also giving me inspiration to continue further down the FEC path, which is especially relevant for the ULV project (putting a scientific instrument on the moon). I might do a post with more information about that on the other blog..

Revision 2016

Went to the Revision demoparty in Saarbrücken this easter, which has become a bit of a tradition. The trip went via a flight to Amsterdam, from which me and four others rented a car and drove the rest of the way. The trip itself went quite well. Didn’t end up producing any entries, which is unusual. But I was not alone – jvb didn’t have anything either, and we both just sort of poked a little at various projects and hung out with people talking about all kinds of things. Knoeki on the other hand was considerably more productive, having two productions entered in the compos and winning third place in the 2D demo competiion (congrats!)

On to the pictures:

Tracked music compo

Tracked music compo

Knoeki's notoriously crusty/heavily modified C64

Knoeki’s notorious modified C64

Nighttime bonfire with people

Nighttime bonfire with people

The winner of the Wild compo, with their gigantic RGB LED display made from a building facade

The winner of the Wild compo, with their gigantic RGB LED display made from a building facade

Tried to grab a shot of the full moon, went so-so

Tried to grab a shot of the full moon, went so-so

Managed to snag a HACKERS poster, for Jupiter 666

Managed to snag a HACKERS poster, for the ill-fated Jupiter 666 system

Didn’t manage to snap many pictures of people this year, for some reason. Maybe next year